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[2/2] Support slim LTO bootstrap

Message ID 1407162587-5210-3-git-send-email-andi@firstfloor.org
State New
Headers show

Commit Message

Andi Kleen Aug. 4, 2014, 2:29 p.m. UTC 
From: Andi Kleen <ak@linux.intel.com>

Add a new bootstrap-lto-slim config file that enables slim (non-fat) LTO
bootstrap. This improves the performance of the LTO bootstrap.

Speeds up the LTO bootstrap by ~18% on a 4 core system.

This requires using gcc-ar/ranlib in post stage 1 builds, so these
are passed to all sub builds.

I made it a new config file for now because it requires the host to support
linker plugins, which I believe is not supported everywhere yet?

config/:

2014-08-04  Andi Kleen  <ak@linux.intel.com>

	* bootstrap-lto-slim.mk: New file.

/:

2014-08-04  Andi Kleen  <ak@linux.intel.com>

	* Makefile.tpl (POSTSTAGE1_HOST_EXPORTS): Add LTO_EXPORTS.
	POSTSTAGE1_FLAGS_TO_PASS):  Add LTO_FLAGS_TO_PASS.
	* Makefile.in: Regenerate.

gcc/:

2014-08-04  Andi Kleen  <ak@linux.intel.com>

	* doc/install.texi: Documentation bootstrap-lto-slim
---
 Makefile.in                  |  2 ++
 Makefile.tpl                 |  2 ++
 config/bootstrap-lto-slim.mk | 13 +++++++++++++
 gcc/doc/install.texi         |  5 +++++
 4 files changed, 22 insertions(+)
 create mode 100644 config/bootstrap-lto-slim.mk
diff mbox

Patch

diff --git a/Makefile.in b/Makefile.in
index 329af7f..af59823 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -256,6 +256,7 @@  POSTSTAGE1_HOST_EXPORTS = \
 	  $(XGCC_FLAGS_FOR_TARGET) $$TFLAGS"; export CC; \
 	CC_FOR_BUILD="$$CC"; export CC_FOR_BUILD; \
 	$(POSTSTAGE1_CXX_EXPORT) \
+	$(LTO_EXPORTS) \
 	GNATBIND="$$r/$(HOST_SUBDIR)/prev-gcc/gnatbind"; export GNATBIND; \
 	LDFLAGS="$(POSTSTAGE1_LDFLAGS) $(BOOT_LDFLAGS)"; export LDFLAGS; \
 	HOST_LIBS="$(POSTSTAGE1_LIBS)"; export HOST_LIBS;
@@ -826,6 +827,7 @@  POSTSTAGE1_FLAGS_TO_PASS = \
 	GNATBIND="$${GNATBIND}" \
 	LDFLAGS="$${LDFLAGS}" \
 	HOST_LIBS="$${HOST_LIBS}" \
+	$(LTO_FLAGS_TO_PASS) \
 	"`echo 'ADAFLAGS=$(BOOT_ADAFLAGS)' | sed -e s'/[^=][^=]*=$$/XFOO=/'`"
 
 # Flags to pass down to makes which are built with the target environment.
diff --git a/Makefile.tpl b/Makefile.tpl
index 4822c32..261461a 100644
--- a/Makefile.tpl
+++ b/Makefile.tpl
@@ -259,6 +259,7 @@  POSTSTAGE1_HOST_EXPORTS = \
 	  $(XGCC_FLAGS_FOR_TARGET) $$TFLAGS"; export CC; \
 	CC_FOR_BUILD="$$CC"; export CC_FOR_BUILD; \
 	$(POSTSTAGE1_CXX_EXPORT) \
+	$(LTO_EXPORTS) \
 	GNATBIND="$$r/$(HOST_SUBDIR)/prev-gcc/gnatbind"; export GNATBIND; \
 	LDFLAGS="$(POSTSTAGE1_LDFLAGS) $(BOOT_LDFLAGS)"; export LDFLAGS; \
 	HOST_LIBS="$(POSTSTAGE1_LIBS)"; export HOST_LIBS;
@@ -631,6 +632,7 @@  POSTSTAGE1_FLAGS_TO_PASS = \
 	GNATBIND="$${GNATBIND}" \
 	LDFLAGS="$${LDFLAGS}" \
 	HOST_LIBS="$${HOST_LIBS}" \
+	$(LTO_FLAGS_TO_PASS) \
 	"`echo 'ADAFLAGS=$(BOOT_ADAFLAGS)' | sed -e s'/[^=][^=]*=$$/XFOO=/'`"
 
 # Flags to pass down to makes which are built with the target environment.
diff --git a/config/bootstrap-lto-slim.mk b/config/bootstrap-lto-slim.mk
new file mode 100644
index 0000000..9e065e1
--- /dev/null
+++ b/config/bootstrap-lto-slim.mk
@@ -0,0 +1,13 @@ 
+# This option enables LTO for stage2 and stage3 in slim mode
+
+STAGE2_CFLAGS += -flto=jobserver -frandom-seed=1
+STAGE3_CFLAGS += -flto=jobserver -frandom-seed=1
+STAGEprofile_CFLAGS += -fno-lto
+
+# assumes the host supports the linker plugin
+LTO_AR = $$r/$(HOST_SUBDIR)/prev-gcc/gcc-ar$(exeext) -B$$r/$(HOST_SUBDIR)/prev-gcc/
+LTO_RANLIB = $$r/$(HOST_SUBDIR)/prev-gcc/gcc-ranlib$(exeext) -B$$r/$(HOST_SUBDIR)/prev-gcc/
+
+LTO_EXPORTS = AR="$(LTO_AR)"; export AR; \
+	      RANLIB="$(LTO_RANLIB)"; export RANLIB;
+LTO_FLAGS_TO_PASS = AR="$(LTO_AR)" RANLIB="$(LTO_RANLIB)"
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 31b8c8b..cac2915 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -2377,6 +2377,11 @@  Enables Link-Time Optimization for host tools during bootstrapping.
 @samp{BUILD_CONFIG=bootstrap-lto} is equivalent to adding
 @option{-flto} to @samp{BOOT_CFLAGS}.
 
+@item @samp{bootstrap-lto-slim}
+Enable slim Link-Time-Optimization for host tools during bootstrapping.
+This is a faster version of @code{bootstrap-lto}, but requires
+the host to support the linker plugin.
+
 @item @samp{bootstrap-debug}
 Verifies that the compiler generates the same executable code, whether
 or not it is asked to emit debug information.  To this end, this